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  1. #1
    SND
    SND is offline Diamond
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    Default OT: Broken Engine Valve, how to prove the cause?

    So, here is the scenario.

    2000 Volkswagen Golf, diesel engine. 108,000KM(about 67,000miles?) goes in for a new water pump and timing belt change at the same time. Car comes out, owner drives about 30km and car stops. Turns out theres a broken valve, it broke at the stem just above the tapered part (I'm no mechanic and don't know the real terms). Dealership says " oh this never happens, it can't be us" and they say over 5000$ to fix it.

    Since in the automotive world a lot of things seem to happen by magic, and it is always" the first time this ever happened."

    What do you guys see as possible causes for 1 valve to break?

    I doubt any pictures were taken of the actual alignment of the belt before the engine was taken apart. So I don't think we can really prove that it was a job done wrong, can we?
    I did google and found another instance that is said to be wrong timing and a valve broke, with pictures included and looks just the same.


    Would a car make it 30kms if the timing was a little off before something breaks?

    So what would you do? is there anything that can be done at all?

    Thanks for any Input.

  2. #2
    MrFluffy is offline Hot Rolled
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    They could have timed it up wrong initially, span the motor round on the starter (as opposed to rotating it by a socket on the pulley by hand for the first few revs), heard this big thunk noise created by the valve catching the piston and bending/being weakened, then re-timed it properly and hoped nobody notices.Unless theres cut marks on the piston crown that would correspond to its position when inside the motor, theres not a lot of ways of proving this.
    Most likely they'd whistle innocently and get away with it and 30kms down the road the now weakened head falls off.

    Ive drove 300kms with a bent valve not seating properly back to my workshop where I could take care of business properly in a needs must situation, but on a renault not a golf...

  3. #3
    Gary E is online now Diamond
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    There are several ways a valve can break, one is to have the timing belt wrong, but if it's wrong, the engine would not run long enough to drive across one curb. The piston would of hit the valve and bent it, then the next hit bends it more and the next hit brakes it. At that time the piston is trapping the broken valve in the combustion chamber and the piston and the cylinder head is dammaged. By that time, the engine has ruined that cylinder and the engine soon stops.. All that takes place in less time than it takes to read this.

    You got 30 km?.. I doubt that you will convince anyone that they assembled the engine wrong.

    Would a car make it 30kms if the timing was a little off before something breaks?
    No.. it would not run 30 seconds, there is NO room for a open valve when the piston is up.

    So what would you do? is there anything that can be done at all?
    I think your in for a rebuild or a engine from a wreck and hope that it works. Just my opinion with somewhat the same experience with a 1980 Olds Diesel after aprox 100,000 miles when it quit.

    My guess is that some or all of the valve springs are weak causing that one valve to stick open and get hit by the piston.

    Is this a engine that has a chain or a belt driving overhead cams? If it is, the chain or belt can stretch delaying the timing a little, or a lot and that causes problems.

    I wish you well with this.

  4. #4
    Carl Darnell is offline Titanium
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    Did it knock before you took it in? Did it knock when you got it? Did it have a slight miss when you got it? It's odd it droped a valve just after the belt change but odd things happen all the time.

  5. #5
    SND
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    This is a friends car, not mine so I wasn't there. I only heard about this yesterday. He did say all was working fine ahead of time. Its not a car that is driven hard by any means.

  6. #6
    Steve in SoCal's Avatar
    Steve in SoCal is offline Stainless
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    This is pure speculation however; a foreign object in the intake tract could break a valve. How does this relate to your car. If the mechanic overlooked a piece of gasket or a bit of crumbled plastic found its way into the manifold it could break a valve. It would be very hard to prove unless the foreign object was still stuck in the cylinder.

    The likelihood of the dealer doing anything is slim but you may try contacting a factory rep, known as zone rep's and see what they say. This seems like a case of; if you didn't have bad luck, you wouldn't have any luck.

    Steve

  7. #7
    aboard_epsilon's Avatar
    aboard_epsilon is offline Titanium
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    find out of its an interference engine or not

    if its non interference ...then its not the garages fault

    if it is an interference engine ...then it is the garages fault ...a good garage would make amends ....a poor one would try to riddle out of it .

    all the best......markj

  8. #8
    Perk is offline Cast Iron
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    More than likely they failed to properly adjust an idler pulley that is intended to provide tension on the timing belt. This would explain why you were able to get a few miles before it broke. I would take it to another authorized mechanic for their opinion, if in agreement with this scenario I would then threaten a lawsuit if not resolved to your satisfaction.

  9. #9
    MikeJB is offline Aluminum
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    You can run an engine with bent valves. We just picked up an engine whose timing belt snapped; a couple of bent valves. The owner fitted a new belt and drove it home; of course it didn't run as well as normal but got him home.

    The engine (Alfa V6) is in fine condition, just two bent valves to replace no other damage.

    We have another Alfa V6 with 8 bent valves.

    It really depends where the valves are when the belt snaps; anything from no damage whatsover to complete disaster.

    A friend who works in a motor spares supply company says he sells a lot of replacement timing belts to people who have had their belt snap very soon after having had a dealer do a routine replacement...............

    Regards,

    Mike.

  10. #10
    Perry Harrington is offline Titanium
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    I've seen valves break without ingesting anything, head just popped off. However, this was after a sprightly jaunt at 5k+ rpms.

    Odds are the engine ingested something. This happens when the intake comes off for service and they leave a nut or something else in the intake, then as you're driving down the road, the nut jolts loose from it's resting spot and gets ingested in the cylinder.

    If it was FOD, the FO should still be in there, or it will show impressions of the FO in the piston or head.

    My bet is they had something in the intake tract. They took the intake off the engine while they did the service and something was dropped and not recovered. Although, most belted engines don't require removal of the intake to get at the belt. However, a water pump job may require that do to screwy routing of coolant lines.

  11. #11
    bruto is offline Stainless
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    I'd be surprised if an interference engine with a belt problem would break a single valve, but I suppose it's possible, since the VW does use an idler for timing belt tensioning, which, as I recall, can be a little tricky. My last experience with an interference engine was when the belt broke on my 12 valve Honda. It bent 9 of them!

    However, unless something has changed since the 90's in the basic layout, you also would likely have to remove a part of the intake manifold for the water pump job, so the possibility that it ingested something remains.

    Many of the speculations I see here are possible, but it's going to be hard to prove anything unless you find something conspicuous, such as a loose idler bolt, or a foreign object in the combustion chamber.

    The other thing that makes me wonder is the quoted price for the repair. If it did simply break a valve, should it be that expensive? Or did the valve head punch out a piston too?

  12. #12
    SND
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    When the valve broke it wrecked everything else anywhere near it. The engine has been replaced with a rebuilt by another mechanic, question now is what to do with this one and if there was anyway to recover costs that have been put on the rebuilt motor.

  13. #13
    Fixed_Gear is offline Aluminum
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    I think Perk is right. The mechanic didn't tension the belt properly. The TDI engine uses an eccentric to tension the timing belt. Insufficient tension would cause the timing belt to slip resulting in bent or broken valves. A properly tensioned belt on a TDI should be able to be twisted 45-90 degrees midway between the camshaft pulley and injection pump pulley. A little bit tighter is better between 45-60 degrees as the belt will stretch with time. But don't over do it, too much tension will put a lot of strain on the injection pump.

    I'm not sure if this will work but you can try it. Take the car to another mechanic and have them put a mark on the tensioner pulley. Then loosen it, put on a new belt and retension the belt to the mark. If the tension is too low then you'll know.

  14. #14
    AeroncaChamp is offline Cast Iron
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    It doesn't seem likely that miss-timed engine would damage only one valve, unless it happened to be the first one to hit the top of a piston when they first turned it over after the repair was completed, and this stopped the engine's rotation. Unless I'm missing something, all the valves of that type (intake or exhaust) would be similarly out of timing.

    Careful post-mortem on the engine might provide a cause - the appearance of the fractured end of the valve stem might offer a clue if it was bent by a collision with the head or had a slow growing fracture. Other possibilities than timing belt - FOD as mentioned, working under cam or lifter or preventing valve from closing. Valve spring breaking or spring clip coming off. High RPMs can cause that kind of failure and can not give the valve time to close before the piston comes back up. Insufficient lube on valve stem leading to galling (sp) and valve freezing in open of semi-open position.

    Without a careful thorough tear down, you'll never know, and even after that you might not get any better clues due to subsequent damage that occurred.

    Is it just me, or does taking a car to the shop always seem to lead to another trip or two to the shop for "totally unrealted" problems?

  15. #15
    bentwrench is offline Cast Iron
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    I would doubt its a problem with timing. Even in an interference engine you can have it off a cog and won't break anything. The engine would run horribly before the timing was off enough to bend a valve. Also if that was the case there would be more than one broken/bent valve. The senario where they discovered the miss-timed belt at start up and re-adjusted it could weaken a valve and give it cause to fail.

    More commonly what I have seen in situations like this is simply a broken spring or a failed keeper. It could just be the motor dropped a valve. It is easy to associate the problem with the work the dealer did, but it might not be the case. You will have a very difficult time getting a warranty repair in the situation described. As far as a VW goes a used engine is going to be the cheapest solution.

  16. #16
    augoldminer is offline Hot Rolled
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    Even a non interference engine can break a valve if you have a dirty injector.
    Diesel engines are high compression and have little clearance.
    A bad injector can cause carbon buildup in the valve clearance area.

    And if the mechanic did not carefully turn the crankshaft and timing gear at the same time it is possible to bend a valve.

    It is unlikely that the timing marks were close so he had to turn the crank to line up the marks for the belt, this should be done carefully with a breaker bar and socket.
    Some mechanics bump the starter on a non interference engine .That is the wrong way to do it,
    If there is carbon build up then you may have interference.

    Check the bolt on the front of the crank to see if a socket was put on it.
    If it is still covered with dirt and shows no sign of a socket the mechanic bumped it and likely that is what bent the valve.

    Take photos.
    And be able to show the judge a mechanics manual showing the proper way to do the job.
    he could win the case if the mechanic did not fallow the manual.
    Or the manual is wrong i have seen this too.

  17. #17
    dkmc is offline Diamond
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    Having driven VW diesels since 1985...and presently driving 1992 Jetta diesel, I have logged nearly 750,000 miles on these power plants.
    Have worked on, and rebuilt these engines also.


    The Piston to Valve clearance in these engines is very tight, INTERFERENCE ENGINE FOR SURE.

    IF the timing was close but not right, there -could- be crescent shaped marks from the valves in the piston heads. Someone needs to retrieve and closely inspect the parts if it's suspect the work was done wrong....

    Aside from that, anything is possible. It could be an error in the work done or simply fatigue in the metal. However, I have never experienced a broken valve or even heard of it happening in this particular engine type.


    Ask your questions on the VW Diesel forum:
    http://www.vwdieselparts.com/forum/index.php

    Good luck


    Take photos.
    YES take LOTS of photos and get the parts and engine back before the parts disappear.....


    And be able to show the judge a mechanics manual showing the proper way to do the job.
    Most likely a waste of time seeing as how the judge probably can't open the hood on his own car or would care to. Rare that a judge would be mechanically inclined enough to understand, or have patience enough to even listen to the explanation......

  18. #18
    d274 is offline Plastic
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    Post this question on TDICLUB forums They have quite a few knowledgable mechanics that should give you good info. I personally would never let A VW dealership in the U.S. near my diesel Jetta. I'm sure there is a few decent diesel mechanics at a couple of dealers but unless your positive they will be doing the work on your car I would not risk it. The above forum has lists of mechanics all over North America that know there way around that particular engine and are always more reasonable. Good luck

  19. #19
    dkmc is offline Diamond
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    I personally would never let A VW dealership in the U.S. near my diesel Jetta.
    Amen to that.....

  20. #20
    bentwrench is offline Cast Iron
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    While it is possible that the dealership caused the problem the burden of proof is not feasible. If they won't fix it under warranty, you are on your own. Your friend's best bet (and this is because I saw it time and time again as a mechanic) is to raise the biggest stink he can. Use words like "un-satisfied" and "disapointed" and "betrayed" (thats a really good one). Make sure to talk to the service writer, then the service manager separately and make sure to use the phrase " I felt like I wasn't being herd by the last guy" (that one is dynamite to a service manager). Don't focus on the details of the problem, infact the less you appear to know the more accepting the service manager will be of your complaint (its called sympathy). Don't swear, don't threaten because people that threatened never got anything fixed. Try everything you can to get them to fix it. If they still won't mabey you can get a compromise, like suggesting you pay for the parts if they cover labor, that has been a good last resort for customers in my experience.

    Good luck

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